Call to mogrify not specifying the format argument

[Deleted user]

I am trying to use this gem. When I use:
respond_to do |format|
format.svg { render :qrcode => request.url}
end

I get this response:
"mogrify -format /tmp/mini_magick20130327-17569-1rwa2n8[0]") failed:

The argument after format is missing.

Any Thoughts?